TARRAGONA, SPAIN—Bienvenido Martínez-Navarro and Policarp Hortolà of the Catalan Institute of Human Paleoecology and Social Evolution speculate that the migration and hunting practices of modern humans may have led to the extinction of the world’s megafauna, and perhaps even the Neanderthals. “No other species has ever developed such a killing potential,” they wrote in the journal Quaternary International. There is no clear evidence that modern humans ever ate Neanderthals, however. “I would not say this has been one of the mainstream arguments for why Neanderthals died out,” commented Chris Stringer of the Natural History Museum in London.